Rotor assemblies for turbines



Dec. 22, 1959 A. MacKAY 2,918,253

ROTOR ASSEMBLIES FOR TURBINES INVENTOR JOHN DAVID A. MqcKAY BY: W4

ATTORNEYS Filed May 18, 1956 2 Sheets-Sheet 1 Dec. 22, 1959 J. D. A. MacKAY 2,918,253

ROTOR ASSEMBLIES FOR TURBINES Filed May 18, 1956 2 Sheets-Sheet 2 IN VE N TOR JOHN DA W0 A. Mac KAY O BWW 0%! ATTORNEYS United States Patent "ice YROTORASSEMBLIES FOR TURBINES John David Alexander MacKay, Toronto, Ontario, Canada, assignor to Orenda Engines Limited, Malton, ntario, Canada, a corporation Application May 18, 1956, Serial No. 585,749 4 Claims. (Cl. 253-49 This invention relates to rotor assemblies for turbine rotors or the like.

In order to mount rotor blades in rotor blade discs, it is conventional to broach slots in the discs and to insert the blade roots of the blades in the slots. Such practice tends to lower the resistance of the disc to centrifugal stress. order to fit accurately in the slots. This greatly increases the cost of assembling the blade discs, especially when blades of plastic material or fibre-glass, which do not easily lend themselves to machining operations, are used.

It is an object of the present invention to obviate these and other disadvantages and to provide a rotor assembly that is cheaply and easily assembled and has a high resistance to centrifugal stress.

It is a further object of the invention to provide a rotor assembly in which rotor blades may be mounted without the need for prior machining of the blade roots.

It is another object of the invention to provide in the rotor assembly means for cooling the rotor disc as well as the blades when the rotor assembly is rotated.

According to the invention, the rotor assembly comprises a ro'tor disc element having a threaded face, a ring element having a threaded face mated with the threaded face of the rotor disc, one of the elements being slotted to receive a pluralty of rotor blades, the other element overlying at least part of each of the slots in the slotted element to hold the blades in the slots, and means for rotating one of said threaded faces relatively to the other.

According to a preferred embodiment of the invention, the rotor assembly comprises a rotor disc having an externally threaded cylindrical flange, a blade ring having an internally threaded flange slotted to receive a plurality of rotor blades and adapted to mate with the threaded flange of the rotor disc, the rotor disc overlying each of the slots in the blade ring to engage the blades and thus hold them in the slots.

The invention will now be described in more detail with reference to the accompanying drawings, it being understood that these are illustrative only and not intended to limit the scope of the invention.

In the drawings, in which each reference character denotes the same part in all the views;

Fig. l is an exploded view of a rotor assembly constructed according to the invention, also showing one form of an assembling or dismantling tool, with a part of the assembly cut off to show an assembling ring on the inside of the blade ring;

Fig. 2 is a fragmentary perspective view of a segment of the roto'r assembly according to the invention, showing the rotor disc and a blade ring in assembled position, and another form of assembling or dismantling tool for use in assembling and dismantling the rotor assembly;

Fig. 3 is a perspective view of one of the blades shown in Figs. 1 and 2; and

Moreover, blade roots must be machined in 2,918,253 Patented Dec. 22, 1959 Fig. 4 is a fragmentary perspective view of a segment of a slightly modified form of the rotor assembly according to the invention. fi

Referring to the drawings, and in particular to Fig. 2 a rotor disc 10 is shown as having a cylindrical disc flange 11 about its external periphery to which is secured a blade ring 12. The flange 11 is provided with screw threads 1111 on its external surface and, along one circumferential edge, with a radially extending flange 11a for a purpose which will be described below. The blade ring 12 comprises a first cylindrical blade flange 13 having screw threads 13b on its internal surface adapted to mate with screw threads 11b on the flange 11 and, along one peripheral edge, is provided with a radially inwardly extending flange 12a. The screw threads may either extend over the entire length of the circumferential surfaces of the flange or may be interrupted according to known threading practice. The hand of the thread is preferably opposite to the intended direction of rotation of the assembly.

The blade flange 13 of the blade ring 12 is pierced at a plurality of circumferentially spaced locations to provide blade mounting apertures 14 extending throughits thickness in a radial direction, the apertures being elongated in the axial direction of the rotor disc, as best shown in Fig. 2, and preferably being tapered radially outwardly so that they have a lesser area on the outer than on the inner circumferential face of the blade flange 13 of the blade ring 12.

Each aperture 14 is adapted to receive a blade 15 having a blade root shaped to co-operate with the blade mounting aperture 14 in the blade flange 13 of the blade .ring 12. Accordingly, each root 15a has a greater crosssectional or lateral dimension at the base or extreme end 156 of the root 15a than at the junction of the root 15a and the blade 15 by being tapered as shown in Fig. 3. The blades therefore may be inserted fromthe inside of the blade flange 13 of the blade ring 12 and are retained in the correspondingly formed blade mounting apertures 14 by the larger base dimension against removal by movement through the apertures in a radially outward direction.

For convenience, removable means are provided to hold the blades 15 temporarily in their apertures in the blade flange 13 while the ring 12 is assembled on the rotor disc; such means may comprise an assembling ring 19 as shown in Fig. 1, preferably of spring wire, adapted to be reduced in diameter and passed under the blade roots 15a and allowed to expand against the inner threaded surface of blade flange 13 to engage the inner faces of the roots 15a and maintain them in position while the ring is being secured to or removed from the rotor disc. The assembling ring 19 need only be kept in position until the blade flange 13 of the blade ring 12 has been threaded onto the disc flange 11 a distance suflicient for the roots 15a of the blades 15 to be positioned over the disc flange 11. The ring 19 may then be removed and the blade flange 1'3 threaded all the way onto the disc flange 11 until the edge 13a of blade flange 13 is in tight abutment with face 11c of flange 11a and face 12d of flange 12a is in abutment with the side face 11d of disc flange 11.

Also for convenience, means are provided for applying a force to the blade ring 12 to screw it onto the rotor disc flange 11. As shown in Fig. 1, a special tool 20 provides lugs 20a'arranged so as to enter slots 21 in the side face of the blade ring, which may form the terminations of pasages 18; a handle 21b on the tool provides sufficient leverage for tightening the blade ring on the rotor disc.

A more convenient means for tightening the elements of the assembly together is shown in Fig. 2; the inner periphery of the flange 12c is provided with an inner circumferential shoulder presenting a ring of teeth 23 which mesh with teeth 25 on a cranking tool 26. The cranking to'ol has a shaft forming on one side a handle 27 and on the other side an axle 26a that may be inserted in a bearing hole 28 in the face of the rotor. Rotation of the cranking tool causes rotation of the ring on the rotor disc until it is tightened or loosened.

Instead of being tapered, as shown in Figs. 2 and 3, the apertures 14 and blade roots 15a may be otherwise shaped to provide a greater cross-sectional or lateral dimension at the base or extreme end of the roots 15a for preventing removal of the blades by outward movement through the aperture; for instance, as shown in Fig. 4, apertures 30 in a blade ring 31 may be stepped inwardly at 32 near the outer face 31a of the ring, and the blade roots 33a of the blades 33 may be correspondingly shaped to engage the step 32 in the slot.

As best seen in Figs. 2 and 4 the rotor assembly of the present invention is particularly adapted for providing air cooled blades and blade mounting structure. A circumferential groove 16 is formed in the threaded surface of the disc flange 11 of the rotor disc and each of .the blades is formed with an open ended passageway 17 extending spanwise through the blade between its outer end 15b and the radially inner face 15c of the blade roots 15a. When a circumferential row of the blades 15 is radially disposed in the apertures 14 the passageway 17 in each blade 15 is in communication with the groove 16 in the rotor disc. Passages 18 extending through the side face of the flange 12a of the blade ring 12 and face 11d of disc flange 11 lead into the groove 16 to transmit cooling air which may be supplied by known structures to the space adjacent the rotor disc. The air entering the groove 16 passes radially outwardly through the passageways 17 in each blade 15.

The foregoing description sets forth the best mode contemplated by the inventor of carrying out his invention, but the following claims are intended to cover all useful changes and modifications of the said mode which are within the scope of the invention.

What I claim as my invention is:

1. A rotor assembly for gas turbine engines comprising a rotor disc having a cylindrical, peripheral disc flange, external screw threads on said flange, a blade ring having a cylindrical blade flange carrying internal screw threads adapted to engage the threads on the disc flange, the blade flange being pierced at circumferentially spaced locations to provide blade mounting apertures of larger crosssection adjacent the inner surface of the blade flange than adjacent the outer surface thereof, a blade in each blade mounting aperture, each blade having a root portion complementary in shape to the shape of the blade mounting apertures so that each blade is retainedin its aperture against radially outward displacement, the threaded surface of the disc flange constituting an abutment for the roots of the blades when the blade flange is threadably engaged thereon to retain each blade against radially inward displacement.

2. A rotor assembly for gas turbine engine as claimed in claim 1 in which the disc flange has, along one peripheral edge, a flange projecting radially outward of the external screw threads on the disc flange against which one edge of the blade flange abuts when it is in threaded engagement with the disc flange.

3. A rotor assembly as claimed in claim 1 including means for rotating said blade ring relatively to the rotor disc comprising a tool having lugs engageable with circumferentially spaced slots in the blade ring and having a handle for turning the tool and with it the blade ring.

4. A rotor assembly as claimed in claim 1 including means for rotating said blade ring relatively to the rotor disc comprising a ring of teeth on the blade flange and a cranking to'ol having teeth adapted to mesh with the teeth on the blade ring and having a shaft providing a handle and an axle, the rotor disc having a bearing hole for the axle of the tool disposed so that when the axle is seated in the bearing hole the teeth on the tool and the blade ring are in operative engagement whereby rotation of the handle rotates the blade ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,603,966 Lorenzen Oct. 19, 1926 2,240,742 Allen May 6, 1941 FOREIGN PATENTS 572,859 Great Britain Oct. 26, 1945 1,080,834 France June 2, 1954 1,105,343 France June 29, 1955 

